低碳钢和铸铁拉伸实验.doc

实验 低碳钢和铸铁拉伸实验设计人：丛金坤学号：071311031指导老师：孔丽海军航空工程学院机械系2011-3-22目录封面1简介2实验3一、实验目的 3二、设备及仪器4三、试件6四、实验原理7五、实验步骤8六、注意事项11七、思考题12附一、英文译文13附二、参考文献30实验 低碳钢和铸铁拉伸实验一、实验目的1.观察低碳钢和铸铁在拉伸破坏过程中的各种现象，并用试验机的自动绘图装置绘制拉伸曲线（PL曲线）2.测定低碳钢的屈服极限s、强度极限B、延伸率和断面收缩率，测定铸铁的强度极限B。3.对实验数据进行分析、归纳、总结的能力。二、设备及仪器1万能材料试验机能进行拉伸、压缩、剪切及弯曲等各种静力实验的试验机称为万能材料试验机（简称为万能机）。这种试验机的牌号很多，型式各异，但一般均由如下三大部分组成，分别为加载系统（提供使试件产生变形的力）、测量系统（量测试件所受的力和产生的变形）、记录系统（自动记录试验曲线的绘图装置）。通常根据加力装置把试验机分为两种类型，液压传动式和机械传动式。液压式万能机的工作原理（图11）是以液压油推动工作油缸4的工作活塞6，并带动与活塞相连的活动台9，以使试件受力并产生变形。图1-1将试件固定于上、下夹头之间，开动油泵5将高压油通过油管（1）压入工作油缸，工作活塞6随即升起，与活塞相连的活动立柱8和工作台9也随之上升，同时带动上夹头10向上移动，这样便使试件受拉力而产生拉伸变形。当进行压缩试验时，将试件置于工作台9上的垫板上，然后活塞上升，试件便受压力而产生压缩变形。加于试件上的载荷大小可由摆锤测力机构来测量。在加载时，工作油缸内的高压油通过另一根油管（2）进入测力油缸14，两个油缸的油压是一样的，此油压通过推动测力活塞15传递给拉杆，由拉杆再通过横杆使摆锤16倾斜，同时，摆上的推杆推动水平齿杆17并带动齿轮旋转，在齿轮轴上装有测力指针，即可在测力度盘上示出载荷的大小。改变摆锤的重量，可以把试验机调节到不同的载荷范围，一般试验机可以更换三种锤重，测力度盘上也相应有三种刻度。如30吨万能机有06吨、015吨、030吨三种测量范围。2游标卡尺三、试件试验表明，试件的尺寸和形状对试验结果会有影响，为了避免这种影响，使各种材料的机械性能数据能相互比较，所以对试件的尺寸和形状，国家标准（GB639786）作了明确规定。试件常用圆形或矩形截面，圆形试件形状如图1-5所示。试件中部长度一般用于测量拉伸变形，称为标距。试件标距部分尺寸的允许偏差和表面加工粗糙度在国家标准中都有规定。试件分为标准试件和比例试件两种。这两种试件都有长短两类，对于圆形截面，长试件L0=10d0，常称为十倍试样，短试件L0=5d0，常称为五倍试件。图1-5在本试验中，所用的低碳钢试件是d010mm的十倍试件。铸铁为脆性材料，受力后变形很小就会突然断裂，并不严格遵守胡克定律。因此，一般只确定其强度极限。而且通常采用L010d0的圆形截面试件。四、实验原理1测定屈服极限s、强度极限b可根据相应的载荷除以横截面原始面积而得到，即：， 2 测定断后伸长率和断面收缩率断后伸长率和断面收缩率分别用下式进行计算：， 其中：L0试件标距原长。L1试件拉断后的标距长度，可将拉断后的试件对紧，然后测量。A0试件横截面的原始面积。A1试件拉断后颈缩处的最小横截面面积。五、实验步骤1 低碳钢的拉伸试验（1）试件准备在试件两端，根据标距长度要求，打两个浅的冲眼作为标距长度的标志，两标志之间的联线应平行于试件的轴线.用游标卡尺在试件的范围内，测量两端及中间等三处截面的直径，要求测量精度至少达到0.02mm，在每一处截面的两个相互垂直方向各测量一次，取其平均值，并取三处截面中最小的平均直径来计算横截面积。（2）试验机的准备操作步骤及注意事项： 选择吨位：在实验前，需估计试件能承受的最大荷载，然后选择试验机的量测范围，挂上相对应的摆锤，并选用相应的测力度盘。 开机调零：开动油泵电机，关闭回油阀。打开送油阀，使工作台空升10mm左右，以消除工作台和活塞等自重的影响，再调测力指针使之对准测力度盘上的零点。 安装试件时，先用上夹头夹紧试件一端，再调整下夹头位置，使上下夹头间的距离适合试件的长度。下夹头的位置调整，可操作另一个电动机的按钮来完成。试件夹紧后，就不允许再调下夹头位置，以免调位电动机烧坏。 调好自动绘图装置。 载入：操作送油阀，使试件加载，加载时要求测力指针匀速平稳地走动，以免试件受到冲击作用。 实验完毕后，关闭送油阀，缓慢打开回油阀。使工作油缸内的油回到油箱，工作台回到初始位置，并卸下外加仪表和取下试件。根据最大载荷的要求，配置合适的摆锤和选用相应的测力度盘，并调整测力指针，对准零点，再拨动从动指针使与主动指针靠近，同时调整自动绘图装置。（3）安装试件先将试件安装在试验机的上夹头内，再移动下夹头使达到适当位置，把试件夹紧。（4）检查及调试:完成上述步骤后，开动机器，预加少量载荷（注意务使应力远小于弹性极限），然后卸载接近零点，以检查试验机、自动绘图装置等工作情况。（5）进行试验开动机器，用慢速加载，使试件缓慢而均匀地产生变形。观察拉伸时测力指标、自动绘图仪的情况。当测力指标回退（或停止不动）时，说明材料发生屈服。记录下测力指针回退到最低位置时的屈服载荷Ps。过屈服阶段后，需继续载入，直至试件断裂为止，停机。并记录由从动指针指示的最大载荷Pb。（6）结束试验取下试件，将断裂试件的两端拼接在一起，用游标卡尺测量拉断后两标志之间的长度L1，并测量颈缩处最小断口直径d1，应在断口两个相互垂直的方向各测量一次，取其平均值，从自动绘图仪上取下拉伸曲线图纸。2铸铁试件铸铁试件的试验步骤与低碳钢试件相似，但比较简单，只要在量出试件截面尺寸d（不需测量标距L）后，将试件安装在试验机上，逐渐加载，使试件断裂，记下最大的载荷Pb即可得出强度极限b。六、注意事项1试验前，务必明确这次试验的目的，测定内容和要求，熟悉操作步骤及有关的注意事项，如有不清楚的地方，要进行研究。讨论或询问指导教师。对与本次实验无关的仪器设备，不得随意乱动。2试验时，必须严格遵守试验机和所用仪器的操作规程。3试验中，如听到异声或发生故障，应立即停机，待排除故障后，再继续加载。4试件安装要正确，防止偏斜或夹入部分过短。5实验结束后，应清理试验设备，整理好所用的仪器及工具。七、思考题1根据实验的现象和结果比较低碳钢和铸铁的力学性能有何不同?2实验中的屈服现象说明了什么问题？附一、英文译文Low carbon steel and cast iron experiment tensile experimentsA, experimental purposes1. Observation low carbon steel and cast iron tensile failure process in the various phenomena, and the automatic drawing device rendering enginery tensile curves (P - L curve)2. Determination of low yield limit sigma s, intensity limit sigma B, elongation delta and section determination of iron, shrinkage intensity limit sigma B.3. The data is analyzed, synthesized and summarized the ability.Second, equipment and instrument1. Universal material testing machineCan stretch, compression, shear and bending, etc. Various kinds of static experiment test enginery called universal material testing machine (referred to as the universal machine). This tester grades many, type varies, but it is composed of the following three major components for loading system respectively, provide make specimen deformation (force), measurement system (quantity test pieces were force and deformation of), recording system (automatic recording test curve graphics device).According to the test enginery strength devices usually divided into two types, hydraulic transmission type and mechanical drive type.The hydraulic universal machine working principle (figure 1-1) is the hydraulic oil cylinder 4 by six, and working the pistons And drive and piston connected platform 9, to make activity deformation force and specimens.Will the specimens under fixed in between, chuck, start by high pressure oil pump 5 will be pressed into the tubing (1) working oil cylinder piston, work with the pistons, six immediately rises connected activity pillar 8 and workbench 9, and with the rising drive chuck 10 moving upwards, that allows caused by tension specimen tensile deformation.When conducting a compression test, will the 9 specimens placed on a table, and then the piston rise on the pad, specimens are generated compression pressure.Add in the load size specimens can be measured by the pendulum agencies to measure strength. In load time, work in high pressure oil cylinder by another root tubing (2) into force measurement oil cylinder 14, two oil cylinders hydraulic is same, the hydraulic force measurement through promoting transfer to bars, piston 15 by rod again through ledger make pendulum 16, at the same time, place on tilt putts gear lever 17 and promoting level driven gear rotating, in the gear axis force measurement can be equipped with Pointers, in measuring strength plate shows the size of the load.Change the weight of the pendulum, can adjust to the different load test enginery, generally range can be replaced three hammer heavy, measuring strength plate also corresponding has three scale. If 30 tons of universal machine have 0 6 tons, 0 15 tons, 0 30 tons of three kinds of measurement range.2. Vernier caliperThree and specimenExperiment shows that the size and shape of the specimen of test results will have effects, in order to avoid this kind of influence, to make all kinds of material mechanical performance data can be compared each other, so for the size and shape of the specimen, national standards (86) GB6397 - clear-cut provisions.Specimen common round or rectangular section specimens, the circular shape as shown in figure 1-5 shows. Commonly used for measuring central length specimens from tensile deformation, called standard. From the part of the specimen standard size allowable deviation and surface roughness implemented in national standards are defined. Specimen of standard test pieces and scale specimens are divided into two. These two specimens have length two kinds, for circular section L0 = 10d0 specimens, long, often called the ten times as samples, short L0 = 5d0 specimens, often called the five times the specimen.In this experiment, the low carbon steel used d0 = 10mm specimens is ten times the specimen. Cast iron is brittle material, mechanical deformation is small will suddenly fracture, not strictly observe the hooker law. Therefore, determine the ultimate strength only commonly. And usually adopts L0 = 10d0 specimens of circular cross sectionFive, the experiment principle1. Determine yield limit sigma s, intensity limit sigma bBut according to the corresponding load cross-section divided by the original area and get, namely:,2. Delta and section determination of elongation epigastric shrinkageEpigastric elongation and section shrinkage is calculated separately in next type:,Among them:L0 - from the original long specimens standard.L1 - from the standard specimens of tensile length, can be pulled to the specimen, then tighten measurement.A0 - cross-sectional primitive area of specimens.A1 - specimens of necking place after ruptured minimum cross section area.Six, experimental steps1. The tensile test low-carbon steel(1) specimen preparationAt both ends, according to standard specimens from length requirements, a dozen two shallow blunt eye as standard length of signs, from between the two marks the on-line should be parallel to the axis of the specimen.The specimens with vernier caliper, within the scope of the measuring three place among both ends and the diameter of the section measurement precision, request to 0.02 mm, at least in each place section two mutually perpendicular direction measuring time, take the average, and to take the youngest of three places section to calculate average diameter cross-sectional area.(2) test enginery of preparationOperating procedures and matters needing attention:(1) the choice before under the experimental tonnage to estimate the largest specimens can withstand loads, then select test enginery measurement range, hang relative should pendulum, and choose corresponding measuring strength plate.(2) the boot zero: actuate the oil pump motor, close return oil valves. Open sent oil valve, around 10mm workbench empty litres, in order to eliminate table and the influence of the piston, etc, and adjustable weight force measurement of efforts on measuring pointer disk zero.(3) when installation, use specimens first collet tight end, adjustments specimens under chuck position, make fluctuation chuck suits in the distance between the length of the specimen. Next chuck position adjustment, operational another motor button to complete. Specimen clamping, were not allowed to attune falls chuck position, lest adjustable bits moters.(4) adjusted the automatic drawing device.(5) : operating sent oil loading specimens valve, when loading, loading force measurement requirements of uniform smoothly walking around, and a pointer to by impact specimens.6 the experiment is finished, close to send oil valve, opened slowly return oil valves. Make work within the cylinder of oil tank, workbench back to back initial position, and remove instrumentation and take off plus specimens.According to the maximum load demand, configuration suitable pendulum and choose corresponding measure and adjust efforts plate force measurement pointer, aimed at zero, then clicked with active pointer driven pointer, and adjustment automatic drawing closer device.(3) installation specimensFirst installed in the test enginery of specimens, within the chuck move again under chuck to reach the proper place, clamping the specimen.(4) check and debug:Complete the above steps, start the machine, pre plus a small load (note unbroken stress is far less than the elastic limit), and unload close to zero to check test enginery, automatic drawing device etc. Work situation.(5) for the testStart the machine, with slow loading, make specimen deformation slowly and evenly. When observing tensile force measurement pointer, automatic plotter. When measuring forces back (or a pointer standstill), explanatory material happen yield. Record pointer measuring forces back to the lowest position of the yield of load Ps.After yield phase, the need for continued until the specimen cracking loading date, stop. And record by the maximum load driven pointer instructions Pb.(6) end testTake down specimens, will fracture specimen together, with both ends joining together after vernier caliper measure tensile length between two logo and measured the L1, necking fracture in the smallest diameter, should be in d1 fracture two mutually perpendicular direction measuring time, take the average, taken from automatic plotter tensile curves drawings.2. Cast iron specimenCast iron specimen test procedures and low carbon steel specimens similar, but relatively simple, as long as there is a specimen section size d (not need measurement standard distance L), will be installed in the experiment on the specimens, gradually loading, make specimen cracking, write down the biggest load intensity limit can draw Pb horizontally b.Seven, the matters needing attention1. Before the test, make it clear this test purpose, determination content and requirements, familiar with the operation procedure and the relevant precautions, such as have not clear place, want to undertake research. Discussion or ask your teacher. Has nothing to do with the experiments of instruments and equipment, do not get optional touch.2. Test enginery, must strictly observe the procedures used instruments with.3. Trials, such as hear different sound or failure, immediately after downtime, stay out fault and then continue loading.4. Specimen installation must be correct, prevent deflection or clip into the part too short.5. Experiment ends, must clean test equipment, good finishing equipment and tools used.Eight, graded1. On the basis of the experimental phenomena and the results compared the mechanical properties of low carbon steel and cast iron have any different?2. The yield phenomenon describes the experiment whats the problem?附二、参考文献1.牛济泰.王式正 焊接基础1987 2.张文钺 金属熔焊原理及工艺 1980 3.王健安 金属学与热处理 1980 4.王泽光 用普通低碳钢焊条补焊灰口铸铁 1999(03)