The NG-1000 - Micro Vickers and Knoop Hardness tester comes standard with a motorized turret and is available in three (3) different configurations to suit all requirements. The primary distinction between graphene-based batteries and solid-state batteries lies in the composition of either electrode. Kelebihan : a. Pengerjaannya lebih mudah dipahami dan dilakukan b. Menghasilkan tegangan uniform di sepanjang penampang c. Harga alat lebih murah d. Waktu pengujian lebih singkat Kekurangan : a. Hanya dapat dipasang pada posisi horizontal b. Spesimen dapat bergeser dari tumpuannya karena tidak dicekam c. Pengujian hanya dapat dilakukan pada . U.S. Department of Energy, Material Science. An adjustable indicator moves over a graduated scale. PP (Polypropylene) Polypropylene is highly common material in manufacturing from furniture to carpets. Option to connect to the latest Electromechanical TestPilot Control Software. The standard to follow depends on the impact testing requirements. This absorbed energy is a measure of a given material's notch toughness and acts as a tool to . GenMooney is a viscosity testing machine is applied to measure the viscosity of the unmixed or mixed unvulcanized natural rubber, synthetic rubber and regenerated rubber .This tester has many functions such as fast warming, maintaining temperature, data stability, etc. Advantages and disadvantages of radial and axial split case pump | Green Mechanic. NG-CoreTrim is used to obtain rock samples perfectly machined (cube, prisms, etc) from irregular rock or core pieces. Delivering the highest level of service to your facility is our mission. 2. DIVIDEND POLICY A dividend policy is a companys way of distributing profits to shareholders. Where Does The Texas Colorado River Start, It has an intelligent power failure recovery system. Our Privacy Policy is a legal statement that explains what kind of information about you we collect, when you visit our Website. Mechanical testing services are a long-established mainstay of the business, and Rotech has a large, well-equipped sample preparation workshop and test house facility. By: Mohamed Adel Mohamadein U.S. Department of Energy, Material Science. The basic Pendulum impact testing machine is an open apparatus. The frame is adjustable for testing samples up to 102 mm dia. Summary In History as Judgment and Promise in A Canticle for Leibowitz, Dominic Manganiello argues that the idea of History within A Canticle for Leibowitz can serve as judgment, promise, and religious bias by examining the close relation between the church and historical memorabilia. They also have a combined Charpy and Izod impact tester for sale. Corrosionpedia is a part of Janalta Interactive. Complete a quick Consumables survey to help NextGen identify how we can benefit you! The SLA process high accuracy, a large variety of material selections, smooth surface finish, and a wide variety of post-processing options making it the perfect choice for a wide range of rapid manufacturing applications, including concept models, rapid prototypes, master patterns, snap-fit for traditional products. . A material's toughness is a factor of its ability to absorb energy during plastic deformation. The principal difference, aside from sample and notch dimensions, is in the configuration of the test setup (Fig 1). While the test is most commonly performed on metals, there are also a number of standards that exist for plastics and polymers, including ASTM D6110 and ISO 179. Izod, Gilbert, 'Testing brittleness of steel', https://en.wikipedia.org/w/index.php?title=Izod_impact_strength_test&oldid=1091339583. A typical testing machine uses a pendulum to strike a notched specimen of defined cross-section and deform it. var essb_settings = {"ajax_url":"http:\/\/www.dreamstr.org\/wp-admin\/admin-ajax.php","essb3_nonce":"e3bacbc073","essb3_plugin_url":"http:\/\/www.dreamstr.org\/wp-content\/plugins\/easy-social-share-buttons3","essb3_facebook_total":true,"essb3_admin_ajax":false,"essb3_internal_counter":false,"essb3_stats":false,"essb3_ga":false,"essb3_ga_mode":"simple","essb3_counter_button_min":0,"essb3_counter_total_min":0,"blog_url":"http:\/\/www.dreamstr.org\/","ajax_type":"wp"};/* generated in /home/dreamstr/public_html/dreamstr.org/wp-content/themes/flow/functions.php flow_elated_page_padding function */ for Izod tests). Despite its small size, the axis of the heavy cast iron frame on which the TensileMill CNC MINI slide on linear rails very smoothly. | Head of the Corrosion, Arab Petroleum Pipelines, | Pipeline Coatings Application Consultant, Crest Industrial Chemicals, | Principal Consultant, Bradley Consulting Services, How To Conduct An AC Attenuation Survey on an Underground Pipeline, Anodize This: The Brilliance of Anodizing, How to Prevent Filiform Corrosion Under Coatings, 8 Things to Know and Understand About Iron Corrosion, Top Corrosion Mitigation Technologies to Watch for in 2021, Troubleshooting Cathodic Protection Systems and Function Systems. The impact value of a material can also change . It is supplied complete with a proper vice to hold irregular pieces firmly in place up to 7x14 cm approximately and "V" device for cores up to 75 mm diameter. Asos Employees Number, Save instructors the time and energy involved in writing test questions. ImPACT Test is a baseline test administered before and after an athlete receives a concussion. Penetration testing describes the process of simulating a cyberattack against a computer system, network, website, or . The machine is used to simulate an environment of sunlight radiation on a specimen to identify the resistance of fabric to discoloration. The test methods are also for metallic materials. Dividend policy only refers to ordinary shares. A more typical stiffness is that of a thin plate in two dimensional bending. Brittle materials have low toughness as a result of the small amount of plastic deformation that they can endure. The unit can test up to four specimens at the same time for abrasion. This machine is designed to get the characteristic curve and characteristic parameters of rubber vulcanization by measuring the applied moment of rubber to the oscillating dye body. The benefits of printing in nylon for our clients far outweigh other 3D printing technologies. We have used Izod impact and Charpy impact tests as part of material qualification programs, comparisons of materials for second source procurement, and to aid in the root cause analysis . Also comes with an option to connect to a PC for advanced software analysis. Why Things Break: Understanding the World by the Way It Comes Apart. Our goal is to ensure that our clients have a positive purchasing experience. From the energy absorbed by the sample, its impact energy is determined. Reynolds, M. B.. . The Izod impact method can test for the toughness of metallic as well as plastic materials. by | Jul 3, 2022 | school teachers friendly trust fund | 71st infantry division ww2 | Jul 3, 2022 | school teachers friendly trust fund | 71st infantry division ww2 3.4 Impact test This test is used to find out the value of impact strength by measuring the energy absorbed by the specimen before failure. The columns refer to the impact frame of the tester. GenDale is mainly used to test shoe fabric, shoe lining, and many other types of shoe related materials. The system is capable of taking a hardness value while a temperature sensor mounted on the bottom of the device is taking a temperature value. Pusey & Jones is a rubber and rubber like material testing plastometer system. After researching different polymers and comparing mechanical properties it was found that Polypropylene polymer was mainly used in manufacturing of bumpers. Such can be approached with a larger radius and deeper V-notch. ISO standards report impact strengths in kJ/m2, where the impact energy is divided by the cross sectional area at the notch. ASTM E23 outlines test methods for notched bar impact testing. ","mejs.time-skip-back":["Skip back 1 second","Skip back %1 seconds"],"mejs.captions-subtitles":"Captions\/Subtitles","mejs.captions-chapters":"Chapters","mejs.none":"None","mejs.mute-toggle":"Mute Toggle","mejs.volume-help-text":"Use Up\/Down Arrow keys to increase or decrease volume. The company offers a Life time consultation advantage. Disadvantages of Plastic-Non-renewable-Permeation (weak barrier properties)-Sorption (loss of flavor into plastic) Izod impact test: used for sheet sample. Why? The Izod test is most commonly used to evaluate the relative toughness or impact toughness of materials and as such is often used in quality control applications where it is a fast and economical test. The NextGen testing frames incorporate precision electromechanical load frame equipment to meet all of your testing needs. Notched Izod impact tests were performed in a Ceast 6545100 Izod impact tester, applying an impact energy of 2.75 J, according to the ASTM D-256 standard. Over the years we have provided our clients with reliable data sets for mission critical decision making. In addition, the article includes information on the instrumentation, standards and requirements, and limitations of instrumented Charpy impact test, which is carried out in specimens with induced fatigue precrack. These impact tests allow designers to compare the relative impact resistance under controlled laboratory conditions and, consequently, are often used for material selection or quality control. Impact testing is a complex and controversial subject, and one that is in the midst of change. Impact test involves the sudden and dynamic application of load to a test specimen. Cleavage can occur in body centred cubic materials, where cleavage takes place along the {001} crystal plane. To carry out this test we have prepare specimen as per the standards. The specimen in the Pendulum Charpy impact tester is a horizontal beam secured on both ends, while the specimen for the Izod impact tester is cantilevered in a vertical position. These rebound testers will determine the dynamic behavior of various materials and supply the differentiation of these materials' qualities. The Cookies Statement is part of our Privacy Policy. This is also designed for Charpy impact strength testing. The Vicat frame consists essentially of a metal stand with a sliding rod. Most standardized tests are created to evaluate the information individual students have retained in core competency areas of learning . Often the assessments can be completed in less time, multiple candidates can complete the online assessment at the same time and there is no need for specialized (and expensive) personnel. The impact results clearly show how different formulations can have the same hardness, yet their impact resistance can vary by as much as 200%. The Charpy impact test is performed to evaluate the resistance of the metal to breakage by flexural shock or impact load according to standard test method ASTM D6110. Technical Teaching Equipment. The max capacity of this tester is 5.5J (Izod) and 5J (Charpy) Advantages. 1. This is a standard method for testing the impact strength of a component containing a stress concentration. As the pendulum strikes the specimen, the breaking energy of the specimen is recorded. DOE Fundamentals Handbook, Volume 1 and 2. The material is tested to determine its impact strength until it yields. This type of behaviour is more prominent in materials with a body centred cubic structure, where lowering the temperature reduces ductility more markedly than face centred cubic materials. Plastic samples are typically a 64 x 12.7 x 3.2 mm bar with a machined V-shaped notch. Results from impact testing are critical in understanding a sample's toughness and predict how much energy it can withstand before failure. HPE III is R&D's latest development of the next generation HPE testing systems. This German-manufactured system has been the global benchmark of Shore hardness testing systems since 1954. The Izod impact test is a standard test that measures the impact energy needed to fracture a material. The major disadvantage is that it is difficult to choose the suitable hardness test method because its result may be different in multiple methods. The other name of the Charpy impact test is the Charpy V-notch test because of the specimen used in this test cut at Charpy test; Izod Test; Procedure and concept behind the two tests is same, the only difference is the type of machine used. EXPERIMENT 1: IZOD/CHARPY TEST Objective 1. .wpb_animate_when_almost_visible { opacity: 1; }(function(w,d){function a(){var b=d.createElement("script");b.async=!0;b.src="http://www.dreamstr.org/wp-content/plugins/wp-rocket/inc/front/js/lazyload.1.0.2.min.js";var a=d.getElementsByTagName("script")[0];a.parentNode.insertBefore(b,a)}w.attachEvent?w.attachEvent("onload",a):w.addEventListener("load",a,!1)})(window,document); Difference Between Izod and Charpy Methods Izod vs Charpy Methods The izod test involved the striker, the testing material, and the pendulum. Open and Enclosed Testers Methods of toughness testing Charpy Impact test Izod impact test 30 31. As entrepreneurs, freelancers and social media moguls rise in the ranks- your rights as a working individual are changing. It can be fit with 300 to 450 mm dia. Impact Testing Through IZOD or Charpy Test. Izod test sample usually have a V-notch cut into them, although specimens with no notch as also used on occasion. Advantages: It is the most rapid method and is fully automated. 11. } Consumerism is still a trend, and powerful commercials are convincing in their attempts to push the latest gadget under the Its 2016, the world is evolving at a seemingly unprecedented rate, and the traditional workforce is a thing of the past. All services are executed by professional certified qualified technicians and quality engineers. 1) You may use almost everything for non-commercial and educational use. In this automatic model, the incremental loading, in the load (stress) or swelling (strain) mode, is fully automatic for a practical and accurate test execution with more reliable test results. However, both use different sample specimen, such as in Izod testing size of the part is 10 10 75 mm, whereas in Charpy test, the specimen size is 10 10 60 mm. Izod Impact test The Izod impact test is a quick and simple test to facilitate a comparative material assessments. Calibration standard is required. Most of the machines are easy to operate with a user friendly interface. The notched impact strength of TX1001 is 950J / M, and the notched impact strength of TX2001 is 650J / M. These properties give the product a better life. These methods employ same machine and yield a quantitative value of the energy required to fracture a special V notch shape metal. Many otherwise satisfactory plastics are rejected for engineering and other applications simply because they have a tendency towards brittle fracture under impact loading. This standard is useful when it is not possible to predict the specimens response prior to the test. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Marketing032022-09-22T11:35:12+01:00May 21st, 2021|accelerated weathering, mechanical testing, UV ageing, uv light test|, ImpactSolutions2022-09-22T12:27:48+01:00April 9th, 2019|Accredited Testing, mechanical testing, physical testing, UKAS|, ImpactSolutions2022-09-22T11:10:10+01:00August 9th, 2018|mechanical testing|, Author1112022-09-22T11:41:39+01:00April 13th, 2018|mechanical testing|, Impact Technology Centre Impact testing condition should simulate the condition at which the sample is expected to operate in. The autoclave has a high-pressure steam vessel measuring about 154 mm dia. This test determines the rate and magnitude of consolidation of a soil specimen restrained laterally and subjected to a number of successive increments of vertical loads. SGS PSI has a dedicated laboratory for physical testing of polymers, plastic, and rubber materials. It has a rapid testing time. In both tests, sample thickness depends on the specifications for the material being tested (typically 1/8 in. Title: The Izod method is an impact testing method given by Gilbert Izod in 1903. Five replicate specimens were tested and averaged for all the mechanical testing values. The striker was fixed at the end of the pendulum. We pride ourselves on providing exceptional quality equipment for the most competitive prices on the market. lb/in2). GenNBS is used to test the abrasion resistance of vulcanized rubber or other rubber compounds. border: none !important; Subscribe to Corrosionpedia for free. box-shadow: none !important; Izod impact is defined as the kinetic energy needed to initiate fracture and continue the fracture until . Toughness of a material can be measured using a small specimen of that material. The APEX 400 is a dedicated solution for manual preparation of pressed pellets for XRF analysis. The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoM.com. The Izod specimen can have up to three notches. DIN 50115 this standard covers notched bar impact bend testing. This type of test is especially valuable in the mining industries, underground construction and various tunnelling excavation processes. The laboratory vane apparatus is based on an original concept of the Transport and Road Research Laboratory of the United Kingdom. In recent years, the IoT is rapidly being introduced into almost all sectors, but it has particular importance in the EV industry. This helps in gathering precise data samples and taking advanced force and energy measurements. It shows surface and near surface defects, and these are the most serious ones as they concentrate stresses. Here at NextGen, we stand behind our products 100%. The standards related to the IZOD impact testing are ISO 180 and ASM D256. An enclosed casing for better protection during impact testing. January 1993. There is a very. January 1993. The specimen fractures at the V-notch due to the impact force applied by the hammer. The impact energy is then calculated from the potential energy transferred from the load to the specimen. The Izod test is most commonly used to evaluate the relative toughness or impact toughness of materials and as such is often used in quality control applications where it is a fast and economical test. Therefore, despite the low-cost of UF relative to the other major wood adhesives these drawbacks limit its usage. Though both the tests follow the same principle, yet they are performed differently. The system is capable of taking a hardness value while a temperature sensor mounted on the bottom of the device is taking a temperature value. This test cover the determination of the consolidated drained shear strength of a soil material in direct shear. Toughness in this context correlates to the materials capacity to absorb energy. We are committed to providing the best after-sales and warranty support to each of our clients. Many materials fail suddenly under impact, at flaws/cracks or notches. compared with < 1.0 ft-lb/in. What is the difference between Charpy and Izod Impact tests? Use the terms and methods that are used in the book. In reality, Izod measures the notch sensitivity rather than being a true impact measurement. Fig 1: Charpy Test Apparatus This test determines the amount of energy absorbed by a material during fracture. ISO and ASTM standards express impact strengths in different units. For example, the notched Izod impact strength of G-PEEK composites with various loadings of graphite/graphene all show increases with respect to the neat polymer (Table 4). 3. To us, communication and personalized service is key. Easy to use instruments with user friendly interfaces and the sample sizes are much smaller - often just a finger prick blood sample or a small volume sample bottle is needed. The servo motor can also apply braking to the pendulum. This testing method was developed in the 1940s by S.B. The measurements are done through volumetric loss of a rotating specimen exposed to the action of a standard grinding wheel. Refer them to NextGen and receive free consumables and discounts on your next purchase if they become a NextGen client! Three test specimens were CNC-machined from the check socket and copolymer raw material sheets. Typically, Charpy Izod impact strength at test temperatures of +23 C (A Izod +23 ) and 45 C (A Izod 40 ) as a function of M w for the bimodal HDPE samples. The figure below, from Mitsubishi Chemical Advanced Materials, depicts the Izod impact strength test apparatus. Both methods compliment Gardner impact. The notch used in the test must be of regular dimensions as it has a great impact on the test results. Such processes may include cold working or precipitation hardening. This also allows the estimation of the brittleness or toughness of the specimens, taking in to account the limitations within the test conditions. The resilience test is a type of destructive test that gives us the toughness measure of a material and indirectly its ductility. Did President Nelson Get Pfizer Vaccine, Disadvantages of penetration testing include potentially causing costly losses of sensitive information, encouraging hackers, or exposing your network to cybercriminals. The standard describes requirements for non- ISO test specimens and also for testing metallic materials. were also in use. William D. Callister, David G. Rethwisch. Digi Test II is an automatic Shore, IRHD and VLRH hardness testing system. Furthermore, the results of Izod impact test results are shown in Figure (10). The Charpy impact test was invented in 1900 by Georges Augustin Albert Charpy (18651945), and it is regarded as one of the most commonly used test to evaluate the relative toughness of a material in a fast and economic way. (a.addEventListener("DOMContentLoaded",n,!1),e.addEventListener("load",n,!1)):(e.attachEvent("onload",n),a.attachEvent("onreadystatechange",function(){"complete"===a.readyState&&t.readyCallback()})),(n=t.source||{}).concatemoji?c(n.concatemoji):n.wpemoji&&n.twemoji&&(c(n.twemoji),c(n.wpemoji)))}(window,document,window._wpemojiSettings); This test helps engineers and scientists assess the fracture properties of a given part or component. Izod test and the Charpy test are commonly performed for determining impact strength of materials. The tests share some similarities and differences as well. The Izod impact strength test is an ASTM standard method of determining the impact resistance of materials. Taylor and Francis Publishing. The ASTM method for izod Impact is D 256. There are two common methods of impact testing namely; Izod test and Charpy test. Experiencing an issue? Please choose an optionSearch EngineTwitterLinkedInFacebookPress/Media OutletsTrade Show/ConferenceReferral. The Charpy test involves three-point loading, where the test piece is supported at both ends as a simple beam. This is often a good indicator of the minimum recommended service temperature for a material. The arm swings down hitting a notched sample, breaking the specimen. This is also referred to as permeation, which is not a strong area of PLA. For ISO, impact strength is the result of the impact energy (also in Joules) divided by the area around the notch. As with the older generations, the test procedure is unchanged where a needle (or a probe) drops freely into a cement sample at regular intervals and in fixed positions. While being the standard for plastics it is also used on other materials. An impact load is then applied via a hammer connected to a raised pendulum. Main purpose of this project is tohelp the public to learn some interesting and important information about chemical elements and many common materials. . These are the regular two wired motors with power and ground. Engineers test the ability of a material to withstand impact to predict its behavior under actual conditions. A NextGen representative will be in touch with you as soon as possible! Izod use Farming hammer as striker where as Charpy use Ball Pin hammer as striker 24 comments: Unknown April 2, 2016 at 11:39 PM izod impact test advantages and disadvantages. By continuing to browse this site you agree to our use of cookies. To perform the Izod impact test, a V-shaped notch is first machined into the test specimen. var mejsL10n = {"language":"en","strings":{"mejs.install-flash":"You are using a browser that does not have Flash player enabled or installed. Metallic samples are typically round 127 x 11.43 mm bar with 1 or 3 machined V-shaped notch (es). Copyright 2023 Periodic Table | All Rights Reserved |, What is Ductile Material Ductile Fracture Definition. An Intro to Pipeline Corrosion in Seawater, The 6 Corrosive Components That Can Be Found in Crude Oil, Controlling Corrosion in Electronic Devices, How to Extend the Service Life of Electric Submersible Pumps, 8 Methods of Coating Thickness Measurement, 5 Most Common Types of Metal Coatings that Everyone Should Know About, An Introduction to the Galvanic Series: Galvanic Compatibility and Corrosion, In Support of Phosphoric Acid Wash for Pipe Coating. on standard single notch and type-X3 specimens. We hope, this article, Izod Impact Test, helps you. The basic models run on standard direct current motors. The resultant curve will show a rapid dropping off of impact energy as the temperature decreases. Material breaks with large plastic deformation (little energy absorption) are known as ductile material. /* ]]> */ padding: 0 !important; Butterworth-Heinemann. The information obtained from the Izod impact test is used to determine how various materials will perform when subjected to impact loading. This state of the art system is developed by the latest R&D technology to meet and exceed the highest quality standards for gelatin capsule testing. Testing was conducted on an Impact Tester-Izod Charpy Tension Impact (Testing Machines Inc; Amityville, New York). A more typical stiffness is that of a thin plate in two dimensional bending. If the impact energy drops off very sharply, a transition temperature can be determined. Current trends will likely shape the future of the industry, which is set to continue to show. Verification of pendulum impact-testing machines. The size of the samples also has a great impact on the test results hence it is essential to choose standard sizes of the specimen. Importance of impact test The primary purpose of performing this experiment is to find whether the material is brittle or ductile. At 20 wt% graphite/graphene loading in PEEK, the notched Izod impact strength is 324% greater than the neat polymer, which is an obvious enhancement that is hard to neglect. This setup offers less protection. Operators use a Pendulum impact testing machine to perform both tests. Operators use a Pendulum impact testing machine to perform both tests. Some of the foremost advantages are. This means that a Pendulum izod impact tester can test for multiple fractures in one specimen. Gucci Blue And Red Thong Sandals, The impact testing is done to determine the strength or toughness of a material like metals, and plastics, etc. Since wear is always a result of abrasion, different test methods have been developed for the simulation of long-term wear. The problem is, while these companies may appear to be helping the environment in the short term, what many fail to address is how they plan on being environmentally conscious in the long run, in other words, how to be sustainable. PROCEDURE:- (a) lzod test. The use of online assessments saves companies a lot of time and money. NextGen's full customizable range of curing chambers has the ability to work with two types of display controllers. An Instron CEAST 9050 testing machine was used to conduct an Izod impact test and to calculate the impact strength of the unstitched and the silk-fiber-stitched woven kenaf-reinforced epoxy composites, as shown in Figure 8. Machines are compliant to industry standard testing methods. MIC Corrosion: How Can Microorganisms Eat Holes in a Metal? It covers requirements for metallic materials as well. The machines operator lifts this pendulum at a certain height and locks it in place. It can be provided with a wide range of vane sizes, although as standard, it is sold with the 12.7 mm square vane and a set of four calibrated springs. At Applied Technical Services (ATS) our experts provide helium leak detection services for companies in various industries. The stress concentration and effective flexure stiffness of an ASTM V-notch Izod specimen is excessive for most cases of plastics use. Search for polyolefins, PVC, engineering plastics, elastomers, etc. Most of the impact energy is absorbed by means of plastic deformation during the yielding of the specimen. 2 Impact energy is the amount of work done to fracture a test specimen. Unfortunately, most of us arent reaping the benefits of said hobbies. The machine provides a continuous direct readout for both the weight and the percentage moisture loss through the entire cycle. The Izod impact testing machine uses a farming hammer styled striker. The Izod impact test is a standard test that measures the impact energy needed to fracture a material. The SHEARMATIC 300 automatic machine is ideal for testing geosyntetics and also soil and other materials that contain large particles of up to 20 mm largest dimension. The measurements are based on the 4th, 5th, and 6th impacts. One is the IZOD test and the second is Charpy Test. Discuss the significance and advantages of impact tests compared with static loading tests. The most common specimen thickness is 3.2mm (0.13in), but the width can vary between 3.0 and 12.7mm (0.12 and 0.50in). We create world-leading educational content about corrosion and how to preserve the integrity of the worlds infrastructure and assets. Metals tend to fail by one of two mechanisms, microvoid coalescence or cleavage. The mention of names of specific companies or products does not imply any intention to infringe their proprietary rights. Of the major wood adhesives,urea-formaldehyde (UF) is the most cost-effective adhesive. They are then immediately removed and tested within seconds of removal from the freezer.