Najkompletnija baza podataka na svetu za materijale
• Ključne prednosti

### Koristi se u najrazličitijim oblastima

• Šta vam nudimo?

• Resursi

### Realizovano

DataPLUS, jedinstveni novi modul sa podacima o koroziji, spojevima, dimenzijama, tolerancijama i prevlakama pomaže još boljem izboru optimalnih materijala!

Kliknite za više detalja.

### Webinari

Overview of Total Materia database 12. januar 2022.

Overview of Total Materia database 13. januar 2022.

• O nama

Total Materia nam je omogućila da rešimo na nedvosmislen način sve probleme koje smo imali u vezi sa pretragom alternativnih materijala u stranim državama. Zahvaljujuci Total Materiji izdali smo stvarnu "međunarodnu" specifikaciju za nabavku čelika u stranim zemljama.

Total Materia ostaje jedino sredstvo koje ćemo koristiti u ove svrhe.

Massimo Manfredini
Bonfiglioli Industrial Gearmotors, Bolonja, Italija

Naša misija je jednostavna;
da Total Materia postane
prvi i jedini
izbor inženjera
širom sveta

Prof. Dr Viktor Pocajt, CEO
Key to Metals AG

# True Stress - True Strain Curve: Part One

Sažetak:

During stress testing of a material sample, the stress–strain curve is a graphical representation of the relationship between stress, obtained from measuring the load applied on the sample, and strain, derived from measuring the deformation of the sample. The nature of the curve varies from material to material.

A typical stress-strain curve is shown in Figure 1. If we begin from the origin and follow the graph a number of points are indicated.

Figure 1: A typical stress-strain curve

Point A: At origin, there is no initial stress or strain in the test piece. Up to point A Hooke's Law is obeyed according to which stress is directly proportional to strain. That's why the point A is also known as proportional limit. This straight line region is known as elastic region and the material can regain its original shape after removal of load.

Point B: The portion of the curve between AB is not a straight line and strain increases faster than stress at all points on the curve beyond point A. Point B is the point after which any continuous stress results in permanent, or inelastic deformation. Thus, point B is known as the elastic limit or yield point.

Point C & D: Beyond the point B, the material goes to the plastic stage till the point C is reached. At this point the cross- sectional area of the material starts decreasing and the stress decreases to point D. At point D the workpiece changes its length with a little or without any increase in stress up to point E.

Point E: Point E indicates the location of the value of the ultimate stress. The portion DE is called the yielding of the material at constant stress. From point E onwards, the strength of the material increases and requires more stress for deformation, until point F is reached.

Point F: A material is considered to have completely failed once it reaches the ultimate stress. The point of fracture, or the actual tearing of the material, does not occur until point F. The point F is also called ultimate point or fracture point.

If the instantaneous minimal cross-sectional area can be measured during a test along with P and L and if the constant-volume deformation assumption is valid while plastic deformation is occurring, then a true stress-strain diagram can be constructed.

The construction should consist of using the equation ε = log (L/L0) for true strain in the elastic and initial plastic regions and the equation ε= log (A0/A) once significant plastic deformation has begun. In practice, however, the equation ε= log (A0/A) is used for the entire strain range since the amount of error introduced is usually negligible. The equation σ = P/A for true stress is valid throughout the entire test.

Accurate construction of a true stress-strain diagram becomes exceedingly difficult if the plastic deformation cannot be assumed to occur at a constant volume.

Finally, it should be mentioned that the neither the true stress-strain diagram nor the engineering stress-strain diagram accounts for the fact that the state of stress within the necked-down region is multiaxial. There is no simple way to account for the effect of this multiaxial state of stress on the material’s response, so it is customarily ignored. A schematic representation of an engineering stress-strain diagram and the corresponding true stress-strain diagram can be found in Figure 2.

Figure 2: Material properties determined from stress-strain diagrams: (a) Engineering stress-strain diagram; (b) determination σ by the offset method; (c) true stress-strain diagram

## Pretražite bazu znanja

Unesite reč za pretragu:

 Pretražite prema Kompletan tekst Ključne reči Naslovi Sažetak

 Ovaj članak pripada seriji članaka. Da biste pročitali više o ovoj temi, kliknite na linkove ispod.

U Total Materia Extended Range obuhvata jedinstvenu kolekciju dijagrama napon-deformacija za nekoliko hiljada materijala, različite vrste termičke obrade i radne temperature. U bazi postoje stvarne i inženjerske krive napon-deformacija za različite vrednosti brzine deformacije.

Pretraga dijagrama napon-deformacija oduzima samo nekoliko sekundi.

Unesite materijal u odgovarajuće polje Brze pretrage. Pretragu možete suziti odabirom zemlje/standarda, a nakon toga kliknite na Pretražite.

Kada odaberete materijal koji Vas interesuje, kliknite na link Dijagrami napon-deformacija da biste videli podatke za odabrani materijal. Broj zapisa o dijagramima napon-deformacija se prikazuje u zagradama pored linka.

Pošto su Total Materia krive napon-deformacija neutralni u odnosu na specifikacije standarda, možete ih pregledati klikom na odgovarajući link u bilo kojoj podgrupi.

Pored krivih napon-deformacija na različitim temperaturama, tačke sa dijagrama su date u formi tabele radi lakšeg kopiranja u, na primer, CAE softver.

Moguće je, takođe, videti dijagrame napon-deformacija na drugim radnim temperaturama.

Da biste ovo uradili, jednostavno unesite novu temperaturu u polje Unesite temperaturu.

Nakon što kliknete na dugme Izračunaj, nova kriva će biti iscrtana, a tačke koje odgovaraju definisanoj temperaturi biće prikazane u tabeli pored. Vidite primer ispod, za temperaturu 250°C.

Imate priliku da isprobate Total Materia bazu podataka. Pozivamo Vas da se pridružite zajednici od preko 150,000 registrovanih korisnika kroz Total Materia Besplatni demo.