鋁合金（比如LY12）的熱處理工藝對其受力的蠕變特性有沒有影響？

1)鋁合金（比如LY12(原)）-為新制GB-2A12變形鋁合金，近似對應的囯外合金牌號 AA 2024,ISO AlCu4Mg1。狀態有 (O,T3,T4,T6,T81).

2)梁在受恒定的力時，其變形并不嚴格恒定，而是隨時間增加而增加和不同熱處理工藝----受控於典型材料力學性能(室溫)。

3)蠕變(Creep)理解為是材料在溫度和應力共同作用下的結果，材料高溫強度與室溫強度不同,除溫度因素及力學因素外，還要考慮時間及介貭因素的影響，高溫下原子擴散能力增大，位錯運動能力增加，空位數量增加，晶體滑移糸改變或增加。室溫下晶界阻礙滑移，增加形變阻力，高溫下晶界會進行滑移，參與變形過程。時效合金中沉淀相粗化，也有助于形變。

4)提供參考:
Excessive Creep Strain (ECS)
Principle
In each point of the structure at which the calculation temperature in any load case is in the creep range, the accumulated equivalent structural creep strain, accumulated over all design lifetimes in the creep regime, shall not exceed 5%.
Until agreement on the design creep constitutive laws, based essentially on data in material standards, is reached, the Principle shall not be used, but the Application Rules shall be used instead.

Equivalent creep strain:
Denoting the components of the creep strain by , the equivalent creep strain is defined by
Application Rule 1: Long creep periods (life fraction rule)

This application rule applies for creep load cases of sufficiently long creep periods with essentially time-independent temperature and with time-independent other relevant actions, such that a calculation with time-independent upper bounds of all relevant actions gives a reasonably good approximation of the structure's creep behaviour. The creep periods shall be long enough such that the influence of initial conditions on the lifetime can be reasonably neglected.

NOTE: In case of doubt, the validity of this pre-supposition should be checked with reasonable constitutive models
The principle is fulfilled, if in each point of the structure at which the calculation temperature in any load case is in the creep regime, the accumulated weighted design lifetime in the creep regime, accumulated over all design lifetimes in the creep regime, does not exceed unity. The weight function shall be the reciprocal of the allowable lifetime for the reference stress determined for the relevant load case,

Determination of the creep design temperature
For each interval of a load case in which the calculation temperature is in any point in the creep regime the creep design temperature shall be specified such that it bounds the calculation temperature from above

NOTE: This creep design temperature, to be specified for each interval of all load cases in which the calculation temperature is in the creep regime, may be specified as a function of space, or space- independent .

Determination of the reference stress
a) Determination of the elastic limit action .
For each interval of a load case, of duration , in which the calculation temperature is in the creep range, the value of the action, or the combination of actions, relevant for creep, shall be determined, which corresponds to the on-set of plastification in the region with calculation temperatures in the creep regime in a design model with

-linear-elastic ideal-plastic constitutive law,
-Mises' yield condition (maximum distortion energy hypothesis)
-material strength parameters and partial safety factors as described in b) below and
-for proportional increase of all actions, with the exception of temperature, which shall be time-independent, and
-a stress free initial state.
b) Material strength parameters and partial safety factors
Material strength parameters (RM) and partial safety factors shall be as in , but
- the reference temperature shall be the creep design temperature, determined with the procedure outlined in ,
-the reference time shall be the (sufficiently long) interval duration ,
NOTE 1: For structures of more than one material the material strength parameters, and their design values, will be space-dependent.
NOTE 2: For structures of one material, the material strength parameters, and their design values, may be space-dependent or space-independent, depending on the choice of the creep design temperature.
c) Determination of the (strain limiting) limit action .
For each interval, of duration , in which the calculation temperature is in the creep range, the maximum value of the action, or the combination of actions, shall be determined which can be carried by the design model with

-linear-elastic ideal-plastic constitutive law,

-Mises' yield condition (maximum distortion energy hypothesis) and associated flow rule,
-a material strength parameters and partial safety factors
and for
- proportional increase of all actions, with the exception of temperature, which shall be time-independent,
-a stress free initial state,
with a maximum absolute value of the principal structural strains less than 5%.
d) Reference stress
For each of these intervals, of duration , the design reference stress is given by
where, in addition to , , as in a), b), c) above, denotes the design value of the relevant action, or the relevant combination of actions. These design values shall be determined for actions other than temperature from specified steady upper bounds of these actions with partial safety factors . The specified steady upper bounds shall bound the actions at least in the relevant interval.
NOTE 3: The reference stress may be space-independent but also space-dependent, depending on the choice of the creep design temperature and on the number of materials, see NOTE 1 and NOTE 2. Since the very same reference time has been chosen, the estimate of creep rupture endurance is space-independent. Therefore, any convenient position may be chosen, e. g. the point of maximum equivalent stress, or the point of maximum temperature, and reference stress and reference temperature in this point used in the determination of the weighted lifetime.

Determination of the weighted lifetime
For each interval of a load case, of duration , in which the calculation temperature is in the creep range, the weight function is given by
where is the allowable lifetime for a stress equal to and a limit strength given by the design strength parameter specified in .
The weighted design lifetime, corresponding to this interval in this load case, is given by

Creep damage indicator
The creep damage indicator is equal to the accumulated weighted design lifetime, is given by the sum of all weighted design lifetimes, summed up over all intervals of all load cases where the calculation temperature is in the creep range,
where the sum extends over all intervals of all load cases, and over all specified (design) occurances of the load cases, in which the calculation temperature is in the creep range.
Application Rule 2: Long, interrupted creep periods
This application rule applies for load cases of sufficiently long creep periods, as in application rule 1, but which are interrupted by action cycles resulting in responses of negligible creep and without plastification,

For such load cases, creep and cyclic periods may be treated separately and the individual interrupted creep periods may be combined into one total (non-interrupted) creep period.
The principle is fulfilled if the creep and cyclic fatigue design check is fulfilled, with the creep damage indicator determined for the total creep period by usage of application rule 1.
Action cycles with negligible creep
Action cycles, which interrupt long creep periods, are considered to be of negligible creep, if the maximum duration of calculation temperatures above
- 400°C for ferritic steels,
-500°C for austenitic steels,
is less than 100 hours.

Action cycles without plastification
Action cycles, which interrupt long creep periods, are considered to be without plastification, if the maximum Mises equivalent stress of the response of the model, described below, to the cyclic actions and with initial conditions, described below, does not exceed the short-term design material strength parameter, described below:
a)The constitutive low of the model shall be linear-elastic with material parameters for a temperature given ).
b)The initial stress distribution shall be the one obtained like in the determination of the limit action , for a reference time, required for the determination of the material strength parameters in), given by the total creep period.
c)The short-term design material strength parameter, with which the maximum equivalent stress is compared, shall be the minimum specified values of
- Rp0,2 / tc for ferritic steels,
- Rp1,0 / tc for austenitic steels,
where tc is the respective temperature at each point and each time.