CN106599397A - Method for detecting non-uniform yield stress of formed thin-walled large-curvature polycarbonate plastic part - Google Patents

Abstract

The invention discloses a method for detecting a non-uniform yield stress of a formed thin-walled large-curvature polycarbonate plastic part, and solves the technical problem of low practicality of an existing method for detecting the non-uniform yield stress of the thin-walled large-curvature plastic part. According to the technical scheme, the method comprises the steps of building a finite element model of the thin-walled large-curvature plastic part; then performing plastic molding finite element simulation; and finally obtaining the non-uniform yield stress of the thin-walled large-curvature plastic part. According to the method, thermal history data of all units of a PC material at different mold temperatures is obtained; the yield stresses of all the units are calculated by depending on a constitutive equation; an impact behavior of the thin-walled large-curvature plastic part is further analyzed and optimized by the mechanical performance; and finally an optimal anti-impact thin-walled large-curvature polycarbonate product is designed, so that the method is high in practicality.

Description

The detection of non-homogeneous yield stress after thin-walled deep camber Merlon plastic injection mo(u)lding Method

Technical field

The present invention relates to a kind of detection method of the non-homogeneous yield stress of thin-walled deep camber plastic, more particularly to a kind of thin-walled The detection method of non-homogeneous yield stress after deep camber Merlon plastic injection mo(u)lding.

Background technology

Thermoplastic polymer Merlon (Polycarbonate, abbreviation PC) is due to its high transparent and resistance to impact etc. Excellent properties so as to become one of irreplaceable new structural material of aerospace field, and be widely used in impact In protection product, including spaceman mask, protective eye lens, cockpit, windshield, vehicle window etc., therefore, analyze PC products The influence factor of impact property becomes particularly important.

Document " Predicting the Long-Term Mechanical Performance of Polycarbonate from Thermal History during Injection Molding[J].Macromolecular Materials and Engineering,2009,294(12):829-838. " have studied the rising with mold temperature, and yield stress also increases immediately Greatly, but, even if mold temperature is constant, the thin-walled deep camber Merlon Plastic part model complicated for, yield stress exist Inhomogeneities in product are sizable and can not be replaced by fixed value σ, the mechanical property of product in forming process Impact to its impact property is particularly important.Injection mo(u)lding is for manufacturing the most widely used side of thermoplastic polymer product Method, in whole forming process, the thermal history from melt to solidification stages can affect the yield stress of PC products.Also, for The product of one complicated shape, thermal history a product diverse location be it is different, and for a product not Same position, the inhomogeneities of its yield stress are sizable.Therefore, the PC product designs for rationally, safe, rationally The inhomogeneities of detection and analysis thin-walled deep camber plastic yield stress are for analysis mechanicalness of the exemplar under the conditions of shock loading Can become particularly important.

The content of the invention

In order to overcome the shortcomings of the detection method poor practicability of the non-homogeneous yield stress of existing thin-walled deep camber plastic, this The bright detection method that non-homogeneous yield stress after a kind of thin-walled deep camber Merlon plastic injection mo(u)lding is provided.The method passes through Thin-walled deep camber plastic FEM (finite element) model is set up, then carries out the limited unit's simulation of injection mo(u)lding, finally carry out thermal history-yield stress Calculate, it is final to obtain the non-homogeneous yield stress of thin-walled deep camber plastic.The present invention is by obtaining PC materials under different mold temperatures The thermal history data of each unit, obtain the yield stress of each unit by constitutive equation, by mechanical property so as to further Analysis and optimize the impact behavior of thin-walled deep camber plastic, final design goes out the poly- carbon of optimized shock resistance thin-walled deep camber Acid ester product, practicality are good.

The technical solution adopted for the present invention to solve the technical problems：A kind of thin-walled deep camber Merlon plastic is molded into The detection method of non-homogeneous yield stress after type, is characterized in comprising the following steps：

Step one, the geometric model using business software ANSYS structure thin-walled deep camber plastics simultaneously carry out material properties tax Value and FEM meshing.

Step 2, based on business software Moldflow, injection mo(u)lding analogue simulation is carried out to thin-walled deep camber plastic, by mould Tool temperature is set as 60 DEG C, 80 DEG C and 120 DEG C successively, obtain under different mold temperatures thin-walled deep camber Merlon plastic each The thermal history data of unit.

Step 3, thin-walled deep camber Merlon plastic injection molding process are equivalent to annealing process, according to time temperature equivalence Principle, constructs a yield stress principal curve, uses formula

Calculate yield stress-annealing time principal curve conversion factor.

In formula, Δ U_aFor experiment parameter, 205kj/mol；R is universal gas constant；T is that the heat of any annealing process is gone through History；T_refFor reference temperature.

Step 4, according to yield stress-annealing time principal curve, use formula

Calculate the accumulation equivalent time of plastic under each mold temperature in injection mo(u)lding cooling procedure.

Thin-walled deep camber Merlon plastic constraint in cooling procedure：

In formula, T_gFor the glass transition temperature of PC；For the accumulation equivalent time of cooling procedure；T_cT () is injection The thermal history of process in which materials.

Step 5, the relation that molding thermal history and yield stress are set up according to yield stress-annealing time principal curve, with public affairs Formula

σ_y=σ_y.0+c·log(t_eff+t_a) (5)

Calculate yield stress.

In formula, σ_y.0, c, t_aTo test fitting parameter.

Experiments verify that, chilling temperature below glassy state temperature, t_aFor 0. therefore, temperature is below glassy state temperature, Yield stress：

Step 6, repeat step three arrive step 5, obtain thin-walled deep camber plastic diverse location under different mold temperatures The yield stress of each unit.

The invention has the beneficial effects as follows：The method is by setting up thin-walled deep camber plastic FEM (finite element) model, then is molded Molding finite element modelling, finally carries out thermal history-yield stress and calculates, and finally obtaining the non-homogeneous surrender of thin-walled deep camber plastic should Power.The present invention is obtained often by constitutive equation by the thermal history data of each unit of PC materials under the different mold temperatures of acquisition The yield stress of individual unit, by mechanical property so as to further analyze and optimize the impact behavior of thin-walled deep camber plastic, finally An optimized shock resistance thin-walled deep camber polycarbonate products are designed, practicality is good.

With reference to the accompanying drawings and detailed description the present invention is elaborated.

Description of the drawings

Fig. 1 is after thin-walled deep camber Merlon plastic injection mo(u)lding of the present invention in the detection method of non-homogeneous yield stress Under same mold temperature at different-thickness different units yield stress.

Specific embodiment

With reference to Fig. 1.The detection side of non-homogeneous yield stress after thin-walled deep camber Merlon plastic injection mo(u)lding of the present invention Method is comprised the following steps that：

Below for the PC material thin wall deep camber plastics of same mold temperature, same plastic institute under diverse location is calculated There is the yield stress of unit.The thin-walled deep camber plastic FEM (finite element) model of the PC materials is 1/3rd circles, and average thickness is 4mm, the performance parameter of its material are as shown in table 1.

The performance parameter of 1 material of table

Step 1, the geometric model using business software ANSYS structure thin-walled deep camber plastics simultaneously carry out material properties assignment And FEM meshing.

Step 2, based on business software Moldflow, injection mo(u)lding analogue simulation is carried out to thin-walled deep camber plastic, by mould Tool temperature is set as 60 DEG C, 80 DEG C, 120 DEG C successively, obtain under different mold temperatures thin-walled deep camber Merlon plastic each The thermal history data of unit.

Step 3, thin-walled deep camber Merlon plastic injection molding process are equivalent to " annealing process ", according to time temperature equivalence Principle, constructs a yield stress principal curve, uses formula

Calculate yield stress-annealing time principal curve conversion factor.

In formula, Δ U_aFor experiment parameter, 205kj/mol；R is universal gas constant；T is that the heat of any annealing process is gone through History；T_refFor reference temperature.

Step 4, according to yield stress-annealing time principal curve, use formula

Calculate the accumulation equivalent time of plastic under each mold temperature in injection mo(u)lding cooling procedure.

Thin-walled deep camber Merlon plastic constraint in cooling procedure：

In formula, T_gFor the glass transition temperature of PC；For the accumulation equivalent time of cooling procedure；T_cT () was to inject The thermal history of material in journey.

Step 5, the relation that molding thermal history and yield stress are set up according to yield stress-annealing time principal curve, with public affairs Formula

σ_y=σ_y.0+c·log(t_eff+t_a) (5)

Calculate yield stress.

In formula, σ_y.0, c, t_aTo test fitting parameter.

Experiments verify that, chilling temperature below glassy state temperature, t_aFor 0. therefore, temperature is below glassy state temperature, Yield stress：

Step 6, repeat the above steps 3 arrive step 5, obtain thin-walled deep camber plastic diverse location under different mold temperatures The yield stress of each unit.

It will be seen from figure 1 that under different mold temperatures Thin Wall Plastic Parts yield stress trend and Comparison of experiment results, coincide Preferably.

Claims (1)

1. after a kind of thin-walled deep camber Merlon plastic injection mo(u)lding non-homogeneous yield stress detection method, it is characterised in that Comprise the following steps：

Step one, using business software ANSYS build thin-walled deep camber plastic geometric model and carry out material properties assignment and FEM meshing；

Step 2, based on business software Moldflow, injection mo(u)lding analogue simulation is carried out to thin-walled deep camber plastic, by mould temperature Degree is set as 60 DEG C, 80 DEG C and 120 DEG C successively, obtains each unit of thin-walled deep camber Merlon plastic under different mold temperatures Thermal history data；

Step 3, thin-walled deep camber Merlon plastic injection molding process are equivalent to annealing process, according to time temperature equivalence principle, A yield stress principal curve is constructed, formula is used

$a_T\left(T\right)=\exp \[\frac{{\mathrm{\ΔU}}_a}{R}\·\[\frac{1}{T}-\frac{1}{T_{ref}}\]\]---\left(1\right)$

Calculate yield stress-annealing time principal curve conversion factor；

In formula, Δ U_aFor experiment parameter, 205kj/mol；R is universal gas constant；T is the thermal history of any annealing process；T_ref For reference temperature；

Step 4, according to yield stress-annealing time principal curve, use formula

$t_{eff}={\∫}_0^t{a}_T^{-1}\left(T\right(t\left)\right)dt---\left(2\right)$

Calculate the accumulation equivalent time of plastic under each mold temperature in injection mo(u)lding cooling procedure；

Thin-walled deep camber Merlon plastic constraint in cooling procedure：

$\begin{array}{cc}T>T_g:& t_{eff}^c=0\end{array}---\left(3\right)$

$\begin{array}{cc}T\≤T_g:& t_{eff}^c={\∫}_0^{t_c}{a}_T^{-1}\left(T_c\right(t\left)\right)dt\end{array}---\left(4\right)$

In formula, T_gFor the glass transition temperature of PC；For the accumulation equivalent time of cooling procedure；T_cT () is in injection process The thermal history of material；

Step 5, the relation that molding thermal history and yield stress are set up according to yield stress-annealing time principal curve, use formula

σ_y=σ_{Y, 0}+c·log(t_eff+t_a) (5)

Calculate yield stress；

In formula, σ_{Y, 0}, c, t_aTo test fitting parameter；

Experiments verify that, chilling temperature below glassy state temperature, t_aFor 0. therefore, below glassy state temperature, surrender should for temperature Power：

${\mathrm{\σ}}_y={\mathrm{\σ}}_{y.0}+c\·\log \left(t_{eff}^c\right)---\left(6\right)$

Step 6, repeat step three arrive step 5, obtain thin-walled deep camber plastic diverse location under different mold temperatures each The yield stress of unit.