低碳鋼和鑄鐵拉伸實驗(共32頁)

1、精選優(yōu)質(zhì)文檔-傾情為你奉上實驗 低碳鋼和鑄鐵拉伸實驗設(shè)計人：叢金坤學號：指導老師：孔麗海軍航空工程學院機械系2011-3-22目錄封面1簡介2實驗3一、實驗?zāi)康?3二、設(shè)備及儀器4三、試件6四、實驗原理7五、實驗步驟8六、注意事項·11七、思考題·12附一、英文譯文13附二、參考文獻·30實驗 低碳鋼和鑄鐵拉伸實驗一、實驗?zāi)康?.觀察低碳鋼和鑄鐵在拉伸破壞過程中的各種現(xiàn)象，并用試驗機的自動繪圖裝置繪制拉伸曲線（PL曲線）2.測定低碳鋼的屈服極限s、強度極限B、延伸率和斷面收縮率，測定鑄鐵的強度極限B。3.對實驗數(shù)據(jù)進行分析、歸納、總結(jié)的能力。二、設(shè)備及儀器1萬能材

2、料試驗機能進行拉伸、壓縮、剪切及彎曲等各種靜力實驗的試驗機稱為萬能材料試驗機（簡稱為萬能機）。這種試驗機的牌號很多，型式各異，但一般均由如下三大部分組成，分別為加載系統(tǒng)（提供使試件產(chǎn)生變形的力）、測量系統(tǒng)（量測試件所受的力和產(chǎn)生的變形）、記錄系統(tǒng)（自動記錄試驗曲線的繪圖裝置）。通常根據(jù)加力裝置把試驗機分為兩種類型，液壓傳動式和機械傳動式。液壓式萬能機的工作原理（圖11）是以液壓油推動工作油缸4的工作活塞6，并帶動與活塞相連的活動臺9，以使試件受力并產(chǎn)生變形。圖1-1將試件固定于上、下夾頭之間，開動油泵5將高壓油通過油管（1）壓入工作油缸，工作活塞6隨即升起，與活塞相連的活動立柱8和工作臺9也隨

3、之上升，同時帶動上夾頭10向上移動，這樣便使試件受拉力而產(chǎn)生拉伸變形。當進行壓縮試驗時，將試件置于工作臺9上的墊板上，然后活塞上升，試件便受壓力而產(chǎn)生壓縮變形。加于試件上的載荷大小可由擺錘測力機構(gòu)來測量。在加載時，工作油缸內(nèi)的高壓油通過另一根油管（2）進入測力油缸14，兩個油缸的油壓是一樣的，此油壓通過推動測力活塞15傳遞給拉桿，由拉桿再通過橫桿使擺錘16傾斜，同時，擺上的推桿推動水平齒桿17并帶動齒輪旋轉(zhuǎn)，在齒輪軸上裝有測力指針，即可在測力度盤上示出載荷的大小。改變擺錘的重量，可以把試驗機調(diào)節(jié)到不同的載荷范圍，一般試驗機可以更換三種錘重，測力度盤上也相應(yīng)有三種刻度。如30噸萬能機有06噸、0

4、15噸、030噸三種測量范圍。2游標卡尺三、試件試驗表明，試件的尺寸和形狀對試驗結(jié)果會有影響，為了避免這種影響，使各種材料的機械性能數(shù)據(jù)能相互比較，所以對試件的尺寸和形狀，國家標準（GB639786）作了明確規(guī)定。試件常用圓形或矩形截面，圓形試件形狀如圖1-5所示。試件中部長度一般用于測量拉伸變形，稱為標距。試件標距部分尺寸的允許偏差和表面加工粗糙度在國家標準中都有規(guī)定。試件分為標準試件和比例試件兩種。這兩種試件都有長短兩類，對于圓形截面，長試件L0=10d0，常稱為十倍試樣，短試件L0=5d0，常稱為五倍試件。圖1-5在本試驗中，所用的低碳鋼試件是d010mm的十倍試件。鑄鐵為脆性材料，受力

5、后變形很小就會突然斷裂，并不嚴格遵守胡克定律。因此，一般只確定其強度極限。而且通常采用L010d0的圓形截面試件。四、實驗原理1測定屈服極限s、強度極限b可根據(jù)相應(yīng)的載荷除以橫截面原始面積而得到，即：， 2 測定斷后伸長率和斷面收縮率斷后伸長率和斷面收縮率分別用下式進行計算：， 其中：L0試件標距原長。L1試件拉斷后的標距長度，可將拉斷后的試件對緊，然后測量。A0試件橫截面的原始面積。A1試件拉斷后頸縮處的最小橫截面面積。五、實驗步驟1 低碳鋼的拉伸試驗（1）試件準備在試件兩端，根據(jù)標距長度要求，打兩個淺的沖眼作為標距長度的標志，兩標志之間的聯(lián)線應(yīng)平行于試件的軸線.用游標卡尺在試件的范圍內(nèi)，測

6、量兩端及中間等三處截面的直徑，要求測量精度至少達到0.02mm，在每一處截面的兩個相互垂直方向各測量一次，取其平均值，并取三處截面中最小的平均直徑來計算橫截面積。（2）試驗機的準備操作步驟及注意事項： 選擇噸位：在實驗前，需估計試件能承受的最大荷載，然后選擇試驗機的量測范圍，掛上相對應(yīng)的擺錘，并選用相應(yīng)的測力度盤。 開機調(diào)零：開動油泵電機，關(guān)閉回油閥。打開送油閥，使工作臺空升10mm左右，以消除工作臺和活塞等自重的影響，再調(diào)測力指針使之對準測力度盤上的零點。 安裝試件時，先用上夾頭夾緊試件一端，再調(diào)整下夾頭位置，使上下夾頭間的距離適合試件的長度。下夾頭的位置調(diào)整，可操作另一個電動機的按鈕來完成

7、。試件夾緊后，就不允許再調(diào)下夾頭位置，以免調(diào)位電動機燒壞。 調(diào)好自動繪圖裝置。 載入：操作送油閥，使試件加載，加載時要求測力指針勻速平穩(wěn)地走動，以免試件受到?jīng)_擊作用。 實驗完畢后，關(guān)閉送油閥，緩慢打開回油閥。使工作油缸內(nèi)的油回到油箱，工作臺回到初始位置，并卸下外加儀表和取下試件。根據(jù)最大載荷的要求，配置合適的擺錘和選用相應(yīng)的測力度盤，并調(diào)整測力指針，對準零點，再撥動從動指針使與主動指針靠近，同時調(diào)整自動繪圖裝置。（3）安裝試件先將試件安裝在試驗機的上夾頭內(nèi)，再移動下夾頭使達到適當位置，把試件夾緊。（4）檢查及調(diào)試:完成上述步驟后，開動機器，預(yù)加少量載荷（注意務(wù)使應(yīng)力遠小于彈性極限），然后卸載接

8、近零點，以檢查試驗機、自動繪圖裝置等工作情況。（5）進行試驗開動機器，用慢速加載，使試件緩慢而均勻地產(chǎn)生變形。觀察拉伸時測力指標、自動繪圖儀的情況。當測力指標回退（或停止不動）時，說明材料發(fā)生屈服。記錄下測力指針回退到最低位置時的屈服載荷Ps。過屈服階段后，需繼續(xù)載入，直至試件斷裂為止，停機。并記錄由從動指針指示的最大載荷Pb。（6）結(jié)束試驗取下試件，將斷裂試件的兩端拼接在一起，用游標卡尺測量拉斷后兩標志之間的長度L1，并測量頸縮處最小斷口直徑d1，應(yīng)在斷口兩個相互垂直的方向各測量一次，取其平均值，從自動繪圖儀上取下拉伸曲線圖紙。2鑄鐵試件鑄鐵試件的試驗步驟與低碳鋼試件相似，但比較簡單，只要在

9、量出試件截面尺寸d（不需測量標距L）后，將試件安裝在試驗機上，逐漸加載，使試件斷裂，記下最大的載荷Pb即可得出強度極限b。六、注意事項1試驗前，務(wù)必明確這次試驗的目的，測定內(nèi)容和要求，熟悉操作步驟及有關(guān)的注意事項，如有不清楚的地方，要進行研究。討論或詢問指導教師。對與本次實驗無關(guān)的儀器設(shè)備，不得隨意亂動。2試驗時，必須嚴格遵守試驗機和所用儀器的操作規(guī)程。3試驗中，如聽到異聲或發(fā)生故障，應(yīng)立即停機，待排除故障后，再繼續(xù)加載。4試件安裝要正確，防止偏斜或夾入部分過短。5實驗結(jié)束后，應(yīng)清理試驗設(shè)備，整理好所用的儀器及工具。七、思考題1根據(jù)實驗的現(xiàn)象和結(jié)果比較低碳鋼和鑄鐵的力學性能有何不同?2實驗中的

10、屈服現(xiàn)象說明了什么問題？附一、英文譯文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

11、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

12、 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 specime

13、n 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

14、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 w

15、ill 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,

16、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 forc

17、e measurement oil cylinder 14, two oil cylinder's 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 ge

18、ar 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

19、 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

20、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 ce

21、ntral 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 l

22、ength 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, mecha

23、nical 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

24、 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 st

25、andard.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)

26、 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 me

27、asuring 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-se

28、ctional 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 correspon

29、ding 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 dis

30、k 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 a

31、llowed 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 experimen

32、t 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 corresp

33、onding 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 re

34、ach 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 test

35、Start 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

36、 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 mea

37、sure 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 instal